Self-propelled electronic device

ABSTRACT

Provided is a self-propelled electronic device in which performance for running over a level difference of a floor surface of a room is improved. 
     The self-propelled electronic device includes: a housing which has a bottom plate; a pair of right and left drive wheel units which support the housing; and a resilient member which resiliently urges the drive wheel units in a direction to project toward a lower side from the bottom plate,
         each of the drive wheel units having a drive wheel and a drive wheel holder which holds the drive wheel to be rotatable around a first shaft center, in which   the drive wheel holder is attached to the housing so as to be rotatable around a second shaft center which is arranged further toward a rear side than the first shaft center and which is parallel to the first shaft center, and   an urging force of the resilient member is applied to the drive wheel units such that a pressing force, which is exerted in a direction perpendicular to a straight line connecting the first shaft center and the second shaft center toward an outer periphery of the drive wheel from the first shaft center, is exerted further toward a front side in a traveling direction than toward a gravity direction of the housing.

TECHNICAL FIELD

This invention relates to a self-propelled electronic device, andspecifically relates to a self-propelled electronic device capable oftraveling on a floor surface having a level difference.

BACKGROUND ART

As a self-propelled electronic device, PTL 1 proposes a self-propelledvacuum cleaner which is provided with a housing having a suction port ina lower surface, a pair of right and left drive wheels for supportingand propelling the housing, a main brush provided in the suction port soas to be rotatable, and a side brush (auxiliary brush) providedfrontward of the main brush in the lower surface of the housing so as tobe rotatable.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No.2012-125652

SUMMARY OF INVENTION Technical Problem

Such a self-propelled vacuum cleaner cleans a floor surface of a roomwhile travelling, but in a case where there is a level difference of thefloor surface, it becomes difficult to run over the level differencewhich is higher than a certain height. For example, in a case where alevel difference between a floor surface and a carpet laid thereon, alevel difference due to a doorsill partitioning rooms, a leveldifference due to flooring laid partially on a tatami mat, or the likeis in a room, and the self-propelled vacuum cleaner has low performancefor running over a level difference, the self-propelled vacuum cleaneravoids the level difference, so that cleaning of an area of a roombeyond the level difference is not performed in some cases.

The invention has been made by considering the circumstances above andprovides a self-propelled electronic device in which performance forrunning over a level difference of a floor surface is improved.

Solution to Problem

Thus, according to the invention, provided is a self-propelledelectronic device, including: a housing which has a bottom plate; a pairof right and left drive wheel units which support the housing; and aresilient member which resiliently urges the drive wheel units in adirection to project toward a lower side from the bottom plate,

each of the drive wheel units having a drive wheel and a drive wheelholder which holds the drive wheel to be rotatable around a first shaftcenter, in which

the drive wheel holder is attached to the housing so as to be rotatablearound a second shaft center which is arranged further toward a rearside than the first shaft center and which is parallel to the firstshaft center, and

an urging force of the resilient member is applied to the drive wheelunits such that a pressing force, which is exerted in a directionperpendicular to a straight line connecting the first shaft center andthe second shaft center toward an outer periphery of the drive wheelfrom the first shaft center, is exerted further toward a front side in atraveling direction than toward a gravity direction of the housing.

Advantageous Effects of Invention

The self-propelled electronic device of the invention is configured suchthat the urging force of the resilient member is applied to the drivewheel unit so that the pressing force, which is exerted perpendicularlyto the straight line connecting the first shaft center and the secondshaft center toward the outer peripheral direction of the drive wheelfrom the first shaft center, is exerted further toward the front side inthe traveling direction than toward the gravity direction of thehousing.

With the configuration, performance of the self-propelled electronicdevice for climbing over a level difference is improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a self-propelled electronic deviceaccording to an embodiment 1 of the invention.

FIG. 2 is a bottom view of the self-propelled electronic deviceillustrated in FIG. 1.

FIG. 3 is a view for explaining arrangement of a drive wheel unit in theself-propelled electronic device of the embodiment 1.

FIG. 4 is a perspective view of the drive wheel unit in the embodiment1.

FIG. 5 is a view for explaining performance of the self-propelledelectronic device for climbing over a level difference, in which (A)illustrates the embodiment 1 and (B) illustrates a comparative example.

FIG. 6 illustrates a drive wheel unit U2 in an embodiment 2, in which(A) is a side view and (B) is a perspective view.

FIG. 7 is a side view for comparing outer peripheral shapes of tireportions of respective drive wheels in the embodiments 1 and 2.

FIG. 8 is a view for explaining performance for climbing over a leveldifference by a trapezoidal convex of the tire portion, which has alarge inclination angle, in the embodiment 2.

FIG. 9 is a view for explaining performance for climbing over a leveldifference by a trapezoidal convex of the tire portion, which has asmall inclination angle.

DESCRIPTION OF EMBODIMENTS Embodiment 1

FIG. 1 is a perspective view of a self-propelled electronic deviceaccording to an embodiment 1 of the invention, FIG. 2 is a bottom viewof the self-propelled electronic device illustrated in FIG. 1, FIG. 3 isa view for explaining arrangement of a drive wheel unit in theself-propelled electronic device of the embodiment 1, and FIG. 4 is aperspective view of the drive wheel unit in the embodiment 1.

In the embodiment 1, exemplified is a case where a self-propelledelectronic device 1 according to the invention is a self-propelledvacuum cleaner which cleans a floor surface by sucking air includingdust on the floor surface and exhausting air from which the dust hasbeen removed, while autonomously traveling on the floor surface wherethe self-propelled electronic device 1 is placed.

The self-propelled electronic device 1 is provided with a disk-shapedhousing 2, and components of a rotary brush 9, auxiliary brushes 10, adust collection box 30, an electric air blower (not shown), a pair ofright and left drive wheels 29, a rear wheel 26, a front wheel 27, acontrol portion including floor surface detection sensors 13 and 19, andthe like are provided inside and outside of the housing 2. Theself-propelled electronic device 1 has a feature of a structure of drivewheel units U1 provided with the drive wheels 29, and the feature willbe described in detail after describing an entire configuration of theself-propelled electronic device 1.

In the self-propelled electronic device 1, a part in which the frontwheel 27 is arranged is a front-side portion, a part in which the rearwheel 26 is arranged is a rear-side portion, and a part in which thedust collection box 30 is arranged is a middle portion, and three wheelsof the pair of right and left drive wheels 29 and the rear wheel 26support the housing 2 at a time of stopping and at a time of travelingon a horizontal surface. That is, the front side means a forwardtraveling direction of the self-propelled vacuum cleaner 1 and the rearside means a backward traveling direction thereof.

The housing 2 is provided with a bottom plate 2 a, which has a roundshape in plan view, having a suction port 6 formed at a position in thefront-side portion near a boundary with the middle portion, a top plate2 b having, in the middle portion, a lid 3 which is openable andclosable when the dust collection box 30 is put in or taken out of thehousing 2, and a side plate 2 c, which has a ring shape in plan view,provided along outer peripheral portions of the bottom plate 2 a and thetop plate 2 b. In the bottom plate 2 a, a plurality of holes throughwhich lower portions of the front wheel 27, the pair of right and leftdrive wheels 29, and the rear wheel 26 project outside from an inside ofthe housing 2 are formed, and an exhaust port 7 is formed near theboundary between the front-side portion and the middle portion in thetop plate 2 b. Note that, the side plate 2 c is divided into two offront and rear, and the front portion of the side plate functions as abumper.

In the inside of the housing 2, a front-side storage chamber for storinga not-shown motor unit, the electric air blower, an ion generationapparatus, and the like is provided at the front-side portion, a middlestorage chamber for storing the dust collection box 30 is provided atthe middle portion, a rear-side storage chamber for storing a controlboard of the control portion which is not shown, a battery, a chargingterminal, and the like is provided at the rear-side portion, and asuction path and an exhaust path are provided near the boundary betweenthe front-side portion and the middle portion. Accordingly, in theself-propelled vacuum cleaner 1 according to the present embodiment, acenter of gravity thereof exists further toward a rear side than a firstshaft center of the drive wheels 29, which will be described below.

The suction port 6 is an open surface of a concave formed in a bottomsurface of the housing 2 (a lower surface of the bottom plate 2 a) so asto face a floor surface. Inside the concave, a rotary brush 9 whichrotates around a rotary shaft center parallel to the bottom surface ofthe housing 2 is provided, and in both of right and left sides of theconcave, auxiliary brushes 10 which rotate around rotary shaft centersperpendicular to the bottom surface of the housing 2 are provided. Therotary brush 9 is formed of brushes erected in a spiral manner on anouter peripheral surface of a roller which is a rotary shaft. Each ofthe auxiliary brushes 10 is formed by providing a brush bundle at alower end of the rotary shaft in a radial manner. The rotary shaft ofthe rotary brush 9 and the rotary shafts of a pair of the auxiliarybrushes 10 are pivoted to a part of the bottom plate 2 a of the housing2 and independently coupled to a motor unit provided in a vicinitythereof via a power transmission mechanism including a pulley, a belt,and the like.

The self-propelled electronic device 1 advances when the right and leftdrive wheels 29 rotate normally in a same direction, retreats whenrotating reversely in a same direction, and turns when rotating indirections opposite to each other. For example, in the case of arrivingat a periphery of a cleaning area and in the case of colliding with anobstruction on a course, the self-propelled electronic device 1 causesthe drive wheels 29 to stop and the right and left drive wheels 29 torotate in directions opposite to each other to change orientation.Thereby, the self-propelled electronic device 1 is able to autonomouslytravel across the whole of an area where the self-propelled electronicdevice 1 is placed or over an entire desired range while avoidingobstructions.

<Drive Wheel Unit and Attachment Structure Thereof>

Each aforementioned drive wheel unit U1 has the aforementioned drivewheel 29, and a drive wheel holder 41 which holds the drive wheel 29 soas to be rotatable around a first shaft center P₁.

The drive wheel 29 has a not-shown wheel portion which sets theaforementioned first shaft center P₁ as a center thereof, and a tireportion 29 a which is attached to an outer periphery of the wheelportion. The tire portion 29 a has a plurality of rectangular convexes29 a ₁ and a plurality of concaves 29 a ₂ in an outer periphery thereof,and has a round shape when viewed from a direction of the first shaftcenter P₁. That is, the tire 29 a is formed in such a manner that twotires in which the rectangular convexes 29 a ₁ and the concaves 29 a ₂are alternately arrayed in a circumferential direction are prepared andstuck together such that, next to the rectangular convexes 29 a ₁ of onetire, the concaves 29 a ₂ of the other tire are positioned. At thistime, since there is no gap, nick, notch, or the like between therectangular convexes 29 a ₁ of the one tire and the rectangular convexes29 a ₁ of the other tire which is adjacent thereto, the tire portion 29a has a round shape when viewed from the direction of the first shaftcenter P₁.

The drive wheel holder 41 is attached to the housing 2 so as to berotatable around a second shaft center P₂ parallel to the first shaftcenter P₁.

More specifically, the drive wheel holder 41 is a gear case which has agear inside thereof and is substantially in a shape of a shoe sole inside view, and has a front portion in which the first shaft center P₁ isarranged and a rear portion in which the second shaft center P₂ isarranged, and has a rearward projecting piece 41 a and a pivotal shaft41 b serving as the second shaft center P₂ in the rear portion.Furthermore, the drive wheel holder 41 has a motor M, which is normallyand reversely rotatable, attached to an inner surface of the rearportion, and is configured so that a rotating force of the motor M istransmitted to the drive wheel 29 via a gear and a not-shown drive shaftwhich is on the first shaft center P₁. In addition, a wheel coverportion 41 d which covers the wheel portion of the drive wheel 29 isprovided in an inner surface of the front portion of the drive wheelholder 41.

The pivotal shaft 41 b is pivoted to a rib inside the housing 2 so as tobe rotatable such that the first shaft center P₁ is arranged at anapproximately middle position of a length in a front and rear directionof the housing 2 and the second shaft center P₂ is arranged furthertoward the rear side than the first shaft center P₁. At this time, aheight H₂ of the second shaft center P₂ from a floor surface K is set tobe lower than a height H₁ of the first shaft center P₁ in a state wherethe drive wheel 29 is in contact with the floor surface K.

Note that, in FIG. 3, a reference sign CP indicates a third horizontalshaft center as a comparative example, which is set at a position higherthan the height H₁ of the first shaft center P₁ from the floor surface Kin a state where the drive wheel 29 is in contact with the floor surfaceK.

Moreover, the drive wheel holder 41 has a protruding portion 41 c whichis drawn toward the first shaft center P₁ by a resilient member S (forexample, a tension spring) at a position higher than the height H₂ ofthe second shaft center P₂ from the floor surface K in a state where thedrive wheel 29 is in contact with the floor surface K and at a positionabove the second shaft center P₂. Note that, the protruding portion 41 chas a hook portion 41 c ₁ at an upper end thereof.

In the case of the embodiment 1, a tension spring is used as theresilient member S, a rear end of the resilient member S is hooked onthe aforementioned hook portion 41 c ₁, and the rear end of theresilient member S is hooked on a hook portion 2 f of a drive wheelcover 2 e provided inside the housing 2.

FIG. 5 is a view for explaining performance of the self-propelledelectronic device for climbing over a level difference, in which (A)illustrates the embodiment 1 and (B) illustrates the comparativeexample.

According to the self-propelled electronic device 1 of the embodiment 1configured as described above, as illustrated in FIG. 3 and FIG. 5(A),when the drive wheel 29 tries to climb over a level difference D betweenthe floor surface K and a floor covering J laid on the floor surface K,the front wheel 27 runs over the level difference D first. Thereby, thehousing 2 is supported by the front wheel 27 and the rear wheel 26. Notethat, instead of the front wheel 27, a projecting portion which has asloped surface in sliding contact with a corner of the level differenceD for climbing over may be provided in the bottom surface of the housing2, or the bottom surface may be in sliding contact with the corner ofthe level difference D (not shown in the figure). In such a case, whenthe self-propelled electronic device 1 climbs over the level differenceD, the housing 2 is supported by the aforementioned projecting portionor bottom surface of the housing, and the rear wheel 26.

In such a state, the drive wheel 29 of the drive wheel unit U1 is notpressed against the floor surface K by the weight of the housing 2 butpressed by an urging force of the resilient member S. That is, by anurging force F of the resilient member S, the drive wheel unit U1 ispressed against the floor surface K with the second shaft center P₂ as afulcrum. At this time, the drive wheel 29 is pressed against the floorsurface K with a pressing force R which is in a direction orthogonal toa line A connecting the second shaft center P₂ and the first shaftcenter P₁.

The pressing force R is expressed as a resultant force of a firstcomponent force R₁ for climbing over the level difference D and a secondcomponent force R₂ which is in a direction orthogonal to the firstcomponent force R₁. In addition, the first component force R₁ isexpressed as a component force on a line connecting a contact point ofthe drive wheel 29 and the corner of the level difference D with thesecond shaft center P₁.

In the case of the comparative example illustrated in FIG. 5(B), aheight of a second shaft center CP is set to be higher than the heightH₁ of the first shaft center P₁ (refer to FIG. 3). Other components inthe comparative example are the same as those of the self-propelledelectronic device 1 of the invention.

In the case of the comparative example, the drive wheel 29 is pressedagainst the floor surface K with a pressing force CR which is in adirection orthogonal to a line CA connecting the second shaft center CPwith the first shaft center P₁. The pressing force CR is equivalent tothe pressing force R in the embodiment 1 of FIG. 5(A) and is expressedas a resultant force of a first component force CR₁ for climbing overthe level difference D and a second component force CR₂ which is in adirection orthogonal to the first component force CR₁. In addition, thefirst component force CR₁ is expressed as a component force on a lineconnecting a contact point of the drive wheel 29 and the corner of thelevel difference D with the second shaft center CP.

The pressing forces R and CR are determined as appropriate byconsidering maximum values Rmax and CRmax of the pressing forces R andCR, with which the self-propelled electronic device 1 is not raised in astate where the self-propelled electronic device 1 is placed on thefloor surface K as in FIG. 3, and variations of the urging force F ofthe resilient member S.

When comparing the embodiment 1 (FIG. 5(A)) and the comparative example(FIG. 5(B)), the following difference is found.

In the case of the embodiment 1, since the line A ascends slightly fromthe second shaft center P₂ toward the first shaft center P₁, thedirection of the pressing force R is inclined slightly to the front sidefrom a direction perpendicular to the floor surface K. Meanwhile, in thecase of the comparative example, since the line CA descends slightlyfrom the second shaft center CP toward the first shaft center P₁, thedirection of the pressing force CR is inclined slightly to the rear sidefrom the direction perpendicular to the floor surface K.

Here, θ and Cθ illustrated in FIGS. 5(A) and (B) are set asθ<Cθ.As described above, in a case where the weight of the self-propelledelectronic device 1 and the variations of the urging force F of theresilient member S are at almost the same degree, the urging force F andan urging force CF are adjusted so that R and CR are set asR=CR.Accordingly,R ₁ =R cos(θ)>CR cos(Cθ)=CR ₁is provided, and R₁>CR₁ is established.

Accordingly, it is found that the first component force R₁ of theembodiment 1, which is the pressing force of the drive wheel 29 againstthe corner of the level difference D, is larger than the first componentforce CR₁ of the comparative example.

When a dynamic friction coefficient between the drive wheel 29 and thecorner of the level difference D is μ and dynamic friction forces areF_(f) and CF_(f),F _(f) =μR ₁ >μCR ₁ =CF _(f)is provided, and F_(f)>CF_(f) is established. That is, when beingcompared, the friction force with respect to the corner of the leveldifference D of the embodiment 1 is larger than that of the comparativeexample, so that it can be said that the embodiment 1 has betterperformance for climbing over a level difference than that of thecomparative example.

As described above, in order to increase the first component force R₁,which is the pressing force of the drive wheel 29 against the corner ofthe level difference D, and improve the performance for climbing over alevel difference, the self-propelled electronic device 1 of theinvention illustrated in FIG. 5(A) is configured such that the height H₂of the second shaft center P₂ is set to be lower than the height H₁ ofthe first shaft center P₁, and the urging force F of the resilientmember S is applied at a position above the second shaft center P₂ inthe drive wheel unit U1.

Note that, since a line of action L connecting the second shaft centerP₂ and the hook portion 41 c ₁ in the embodiment 1 is longer than a lineof action CL connecting the second shaft center CP and the hook portion41 c ₁ in the comparative example, in the embodiment 1, it is possibleto reduce the urging force F of the resilient member S (tension spring)compared to that of the comparative example in order to obtain thepressing forces R and CR at almost the same degree. That is, whencomponents of the urging forces F and CF of the resilient member S(tension spring), which is in a direction tangent to a circle having thesecond shaft center P₂ as a center thereof are F_(R) and CF_(R), due tobalance of moments,A×R=L×F _(R) andCA×CR=CL×CF _(R),are provided, and moreover, since A=CA and R=CR are provided,L×F _(R) =CL×CF _(R)is provided, and when L>CL, F_(R)<CF_(R) is established. Here, when theurging force F of the resilient member S (tension spring) is close tothe direction tangent to the circle having the second shaft center P₂ asthe center thereof, it is possible to approximate to F═F_(R) andCF═CF_(R). Accordingly,F<CFis provided. In this manner, it is possible to reduce the urging force Fof the resilient member S (tension spring), thus making it possible toreduce the size of a spring and improve workability at a time ofattachment.

Embodiment 2

According to the present embodiment, even in a case where the center ofgravity of the self-propelled electronic device 1 is further toward therear side than the first shaft center P₁ of the drive wheel 29, it ispossible to improve the performance of the drive wheel 29 for climbingover a level difference. That is, in a case where the center of gravityof the self-propelled vacuum cleaner 1 is further toward the rear sidethan the first shaft center P₁ of the drive wheel 29, even when thedrive wheel 29 reaches the corner of the level difference D and a sideof the housing 2, which is further toward a front side than the drivewheel 29, climbs over the level difference D, a side of the housing 2,which is in the rear side where the center of gravity still remains,does not climb over the level difference D, so that it is stronglyrequired to improve the performance for climbing over a level differenceby the drive wheel 29. As described above, according to the presentembodiment, even in a case where the center of gravity of theself-propelled electronic device 1 is further toward the rear side thanthe first shaft center P₁ of the drive wheel 29, it is possible toimprove the performance of the drive wheel 29 for climbing over a leveldifference, so that flexibility of a layout of an inside of the housing2 is improved. However, also in a case where the center of gravity ofthe self-propelled electronic device 1 is further toward the front sidethan the first shaft center P₁ of the drive wheel 29, according to thepresent embodiment, the performance for climbing over a level differenceis similarly improved.

Embodiment 3

FIG. 6 illustrates a drive wheel unit U2 in the embodiment 2, in which(A) is a side view and (B) is a perspective view. FIG. 7 is a side viewfor comparing outer peripheral shapes of tire portions of respectivedrive wheels in the embodiments 1 and 2. FIG. 8 is a view for explainingperformance for climbing over a level difference by a trapezoidal convexof the tire portion, which has a large inclination angle, in theembodiment 2, and FIG. 9 is a view for explaining performance forclimbing over a level difference by a trapezoidal convex of the tireportion, which has a small inclination angle. Note that, in FIGS. 6(A)and (B), the same reference signs are assigned to elements similar toelements in FIGS. 3 and 4.

The embodiment 2 is different from the embodiment 1 only in a drivewheel 129 of the drive wheel unit U2, and other configuration in theembodiment 2 is similar to that of the embodiment 1.

More specifically, the drive wheel 129 has a not-shown wheel portion anda tire portion 129 a which is attached to an outer periphery of thewheel portion. The tire portion 129 a has a plurality of trapezoidalconvexes 129 a ₁ and a plurality of concaves 129 a ₂ in an outerperiphery thereof, and has the outer periphery with a concave-convexshape when viewed from a direction of the first shaft center P₁.

That is, the tire 129 a is formed in such a manner that two tires inwhich the trapezoidal convexes 129 a ₁ and the concaves 129 a ₂ arealternately arrayed in a circumferential direction are prepared andstuck together such that, next to the trapezoidal convexes 129 a ₁ ofone tire, the concaves 129 a ₂ of the other tire are positioned. At thistime, since there is a V-shaped gap between the trapezoidal convex 129 a₁ of the one tire and the trapezoidal convex 129 a ₁ of the other tirewhich is adjacent thereto, the tire portion 129 a has the outerperiphery with the concave-convex shape when viewed from the directionof the first shaft center P₁.

Further, the trapezoidal convex 129 a ₁ of the tire portion 129 a has anupstream-side inclination surface 129 a ₁₁ in, with a radial line G fromthe first shaft center P₁ as a boundary, an upstream side Us when thetire portion 129 a rotates in a forward traveling direction (directionof an arrow), and has a downstream-side inclination surface 129 a ₁₂ ina downstream side Ds.

With respect to the radial line G, the downstream-side inclinationsurface 129 a ₁₂ is set to have an inclination angle larger than that ofthe upstream-side inclination surface 129 a ₁₁. In other words, theupstream-side inclination surface 129 a ₁₁ is set close to beingparallel to the radial line G as compared to the downstream-sideinclination surface 129 a ₁₂.

Meanwhile, the rectangular convex 29 a ₁ of the tire portion 29 a of theembodiment 1 has perpendicular surfaces 29 a ₁₁ and 29 a ₁₂, which aresubstantially parallel to the radial line G, in both sides having theradial line G from the first shaft center P₁ as a boundary.

According to the self-propelled vacuum cleaner of the embodiment 2,since the tire portion 129 a has the outer periphery with theconcave-convex shape when viewed from the direction of the first shaftcenter P₁, the concaves and the convexes in the outer periphery of thetire portion 129 a easily catches the level difference D, which enablesa rotating force of the tire portion 129 a to be effectively utilizedfor a force in a direction of running over the level difference D.

In addition, as illustrated in FIG. 8, since the downstream-sideinclination surface 129 a ₁₂ of the trapezoidal convex 129 a ₁ of thetire portion 129 a is set to have a large inclination angle α withrespect to the radial line G, the rotating force of the tire portion 129a is able to be effectively used for the force in the direction ofrunning over the level difference D. That is, a notch angle of a grooveis adjusted so that the tire portion 129 a is in surface(downstream-side inclination surface 129 a ₁₂) contact with a topsurface of the level difference D. In addition, by setting theinclination angle α to be large, a distance W₁ by which the trapezoidalconvex 129 a 1 is able to be hooked on the level difference D becomeslong, so that the trapezoidal convex 129 a ₁ is easily hooked on thelevel difference D deeply. Accordingly, it is effective, for example,when the self-propelled electronic device climbs over a doorsill whichhas a corner part abraded to be rounded.

Meanwhile, as illustrated in FIG. 9, in a case where the downstream-sideinclination surface (dotted part) of the trapezoidal convex 129 a ₁ ofthe tire portion 129 a is set to have a small inclination angle β withrespect to the radial line G, since a distance W₂ by which thetrapezoidal convex 129 a ₁ is able to be hooked on the level differenceD becomes short, it becomes difficult to effectively use the rotatingforce of the tire portion 129 a for the force in the direction ofrunning over the level difference D and it becomes difficult for thetrapezoidal convex 129 a ₁ to be hooked on the level difference Ddeeply.

Accordingly, in the self-propelled vacuum cleaner of the embodiment 2,the performance for climbing over a level difference is improved more.Note that, in the case of the embodiment 2, assumed is the case ofclimbing over the level difference D having a height DH of 15 to 20 mm.

Embodiment 4

Though, a case where the self-propelled electronic device 1 is theself-propelled vacuum cleaner which has a cleaning function has beenexemplified in the embodiments 1 and 2, the self-propelled electronicdevice of the invention may be a self-propelled ion generation apparatuswhich has a function of generating ions.

Overview

A self-propelled electronic device of the invention includes: a housingwhich has a bottom plate; a pair of right and left drive wheel unitswhich support the housing; and a resilient member which resilientlyurges the drive wheel units in a direction to project toward a lowerside from the bottom plate,

each of the drive wheel units having a drive wheel and a drive wheelholder which holds the drive wheel to be rotatable around a first shaftcenter, in which

the drive wheel holder is attached to the housing so as to be rotatablearound a second shaft center which is arranged further toward a rearside than the first shaft center and which is parallel to the firstshaft center, and

an urging force of the resilient member is applied to the drive wheelunits such that a pressing force, which is exerted in a directionperpendicular to a straight line connecting the first shaft center andthe second shaft center toward an outer periphery of the drive wheelfrom the first shaft center, is exerted further toward a front side in atraveling direction than toward a gravity direction of the housing.

The self-propelled electronic device of the invention may have followingconfigurations which may be combined as appropriate.

(1) In a state where the drive wheel is in contact with a floor surface,a height of the second shaft center from the floor surface may be set tobe lower than a height of the first shaft center.

In such a configuration, compared to a case where the height of thesecond shaft center from the floor surface is set to be higher than theheight of the first shaft center, and the urging force of the resilientmember is applied to a position above the second shaft center in thedrive wheel units, a force with which the drive wheel presses a cornerof a level difference while traveling forward increases, so thatperformance of the self-propelled electronic device for climbing over alevel difference is improved. This effect of the invention is effectiveparticularly in a case where a center of gravity of the self-propelledelectronic device is in a rear portion thereof.

(2) The drive wheel holder may have, in a position above the secondshaft center, a protruding portion to which the resilient member isattached and which is drawn toward the first shaft center.

This provides an advantage that it is possible to arrange the resilientmember in a space inside the housing, where the drive wheel units arearranged.

(3) The drive wheel may have an outer periphery with a concave-convexshape when viewed from a direction of the first shaft center.

Since it becomes easy for concaves and convexes of the outer peripheryof the drive wheel to be hooked on the level difference, frictionalresistance between the drive wheel and the level difference increases,so that the performance of the self-propelled electronic device forclimbing over a level difference is improved more.

(4) The self-propelled electronic device may be a self-propelledelectronic device which has a cleaning function or a self-propelled iongeneration apparatus which has a function of generating ions.

Accordingly, it is possible to obtain the self-propelled electronicdevice or the self-propelled ion generation apparatus of whichperformance for climbing over a level difference is improved.

Note that, the disclosed embodiments are to be considered in allrespects only as illustrative and not restrictive. The scope of theinvention is indicated by the scope of Claims rather than theabove-described description, and intended is that changes within themeaning and range of equivalency of scope of the Claims are included.

REFERENCE SIGNS LIST

-   -   1 self-propelled electronic device    -   2 housing    -   2 a bottom plate    -   29, 129 drive wheel    -   41 drive wheel holder    -   41 c protruding portion    -   H₁, H₂ height    -   K floor surface    -   P₁ first shaft center    -   P₂ second shaft center    -   S resilient member    -   U drive wheel unit

The invention claimed is:
 1. A self-propelled electronic device,comprising: a housing which has a bottom plate; a pair of right and leftdrive wheel units which support the housing; and a resilient memberwhich resiliently urges the drive wheel units in a direction to projecttoward a lower side from the bottom plate, each of the drive wheel unitshaving a drive wheel and a drive wheel holder which holds the drivewheel to be rotatable around a first shaft center, wherein the drivewheel holder is attached to the housing so as to be rotatable around asecond shaft center which is arranged further toward a rear side thanthe first shaft center and which is parallel to the first shaft center,and an urging force of the resilient member is applied to the drivewheel units such that a pressing force, which is exerted in a directionperpendicular to a straight line connecting the first shaft center andthe second shaft center toward an outer periphery of the drive wheelfrom the first shaft center, is exerted further toward a front side in atraveling direction than toward a gravity direction of the housing. 2.The self-propelled electronic device according to claim 1, wherein in astate where the drive wheel is in contact with a floor surface, a heightof the second shaft center from the floor surface is set to be lowerthan a height of the first shaft center.
 3. The self-propelledelectronic device according to claim 1, wherein the drive wheel holderhas, in a position above the second shaft center, a protruding portionto which the resilient member is attached and which is drawn toward thefirst shaft center.
 4. The self-propelled electronic device according toclaim 1, wherein the drive wheel has an outer periphery with aconcave-convex shape when viewed from a direction of the first shaftcenter.
 5. The self-propelled electronic device according to claim 1,wherein the self-propelled electronic device is a self-propelled vacuumcleaner which has a cleaning function or a self-propelled ion generationapparatus which has a function of generating ions.